Terahertz (THz) waves for electromagnetic radiations is a frequency unit in the range of 0.3 to 3 THz, suitable for applications with frequencies bounded between a high frequency edge (300 GHz) of millimeter wave band and a low frequency edge (3000 GHz) of far-infrared spectral band edge, where the wavelengths corresponding to this frequency range are from 1 mm to 0.1 mm (or 100 μm), respectively. At present, the THz radiation has reached the following consensus internationally: THz is a new radiation source with many unique advantages. THz technology is a very important cross frontier, offering opportunities for new technological innovations, economic developments, and national security applications. Aside from its vast range of applications, the reasons THz technology is attracting widespread attentions is firstly, because the THz spectrum (including the transmission spectrum and the reflection spectrum) of substances contains a wealth of physical and chemical information, therefore this frequency spectrum contains important information of the nature and structures of substances; secondly, because a THz light source has unique transmission and reflection properties compared to traditional light sources.
In recent years, thanks to the rapid development of ultrafast laser technology, excitation light source for THz pulse have become more stable and reliable, fueling the grounds for further studies of THz technology. In addition, THz imaging technology has been highly valued by governments, research institutions, universities and other research institutions. In addition to the development of pulsed THz imaging technology, continuous-wave THz imaging technology, including active and passive imaging techniques, are the subjects of extensive research. In particular, THz imaging techniques have been, to some extent, put to use in security detections and security inspections in key sectors. Meanwhile, various kinds of THz radiation sources, detectors, and some elements with critical functions are also being rapidly developed, which laid the foundation for the applications of the THz technology in chemistry, biology, material, petroleum, chemical engineering, communications, and other fields particularly in the military and security.
Therefore, there are considerable needs for THz electromagnetic wave systems with built-in high absorption housings, such that these systems effectively transmits/receives THz electromagnetic waves while eliminating the interference from unwanted noises.